I dont think its its common.
Thats things happen in only porns..in realistic its really pervert thing...and dont think so pervert. First of all u r keepin relation with married woman and still fantisizing for doubles..stop this pervert things...it may ruin ur life

Two questions underly ur single question. Lets analyse them separately...

First, about group sex ( in this case, 2 males and a female ).. its normal if everyone involved and of equal consent for the act. Sexual practices... almost all of them are dependant on this single factor.. Mutual consent of the ppl involved in it...

Is it normal in india?? I would say not so much... but that doesnt mean ur case is unique.. many indian couples are looking for a sex partner (both male and female) to indulge in group sex with..so u r safe to assume that its not uncommon...

Second, you happened to mention that ur partner (the girl) is not ready for this and u r planning to force her for the act. I would seriously advise against that because these things when seen in porn movies are not that fun in practical... most indian girls are reserved against such deeds..

ask urself a question.. what if she finds it repulsive and that affects ur relationship with her and she decides to leave u?? what if she found the new guy more suitable for her and decides to ditch u??? Consider these things before making a decision...

Finally, never ever force a girl to do something that she doesnt want to do unless u r 100 percent sure she will like it later on... Ask her politely... show some movies which include group sex.. tell her the pros and cons.. and ask her if she is willing for it.. if so go ahead....

Two ways to look at the question, you are asking if MMF threesome is common and secondly whether you should go for it.

In this culture or other cultures also, threesome is not common. Unless its a porno movie, which is made to ignite your sexual desire, or unless the lady is getting money for the service, threesome is not common. Don't believe in Savita Bhabi comics, thats also porno is comics form. I have seen different part of the world, spoken with people, I found they are always comfortable with only two at a bed.

Second part is about you. Its your fantasy to have threesome with your married girlfriend. When a sex occurs, it should be consenting and both should agree to the act. If she is not consenting and being forced to do something, its not good for future sex encounter. If she is not comfortable, dont force. Full stop.
You hava a fantasy to fulfill, have you asked about her fantasy? Maybe she has a fantasy of MMF threesome where you fuck her pussy and the other guy is fucking your ass. If she forces you, would you jump on her idea? Or maybe she has a fantasy of pegging you, like insert some object or her fist on you arse... ouch, doesn't that hurt? If that hurts, dont try anything where consent is missing.
I hope I could explain, if I have failed to, extremely sorry bro.

If you are so fantasized about threesome with your girl friend and other male, drop this idea. If you can not control, you can just ask your male friend to come with his girl friend too. Both of you can enjoy by properly exchanging your girl friends on two different beds in the same room same time. Every one will have recurrently growing excitment to watch the exchanged pairs in fully compromised swing. This will relax you all four at a time. Threesome is unnatural.

Three some is great if done with proper care, the 2nd male should be your fast friend and you should not emotionally attached to that girl. Because it may happen that you lose her and believe me if I were you I will be ready to lose her to get a 3 some exp. once I enticed g.f. Of my friend, he only fucks her and I was also at the verge of fucking her but he didn't allow me to flirt with her. He was feared that he might lose her. So I gave up the idea and only once I brought his g.f. In my room and she only allow oral sex not vaginal.

Threesome sex is extremely uncommon in our country... Threesome sex can be performed with a call girl easily.. But I don't think your gf will be agreed for this..if she does not know your male friend how she would agreed to be fucked by him by force??
Some females may have such desire but after marriage they enjoy their sexual life with her hubby.. If still not satisfied one female can go for extramarital affairs with a male well known to her but she wouldn't like to take much more risk with males who is not known to her(the male may be your intimate friend).. because she generally think if she would do a threesome with you and your friend
.another day a new male may come with you or with your male friend...and she is likely to be blackmailed by them on later or the secrecy would be revealed in public...
Its yours choice do convince her to do threesome sex..you may do with a call girl if your gf is not allow you both to do threesome...